The present invention relates generally to a method and apparatus for EGM signal display and recording, and more particularly to a system for sampling EGM data. The system is particularly well adapted for use in a pacer system analyzer, which may have a small battery operated plotter of limited slew rate capability.
To assist physicians in treating cardiac disorders of the type for which the use of implantable cardiac pacers is indicated, pacer system analyzers (PSA's) have been developed. These devices are used at the time of pacer implantation to efficiently measure the parameters of a pacer system, including a patient's heart, a pacer to be implanted, and implanted pacer leads, without the need to perform separate procedures requiring multiple interconnections and an undesirably long time period to complete. Pacers to be implanted are tested for proper programming and operation, not only while connected in a simulated pacing system environment, but also while operating in the actual system in which they are to be used. Moreover, pacer system analyzers are preferably equipped to generate pacing pulses as required to support the patient during the pacer implantation, independently of the pacer to be implanted.
By using a pacer system analyzer, a physician is able to adjust the operating parameters of a pacer system as required to suit the specific needs of an individual patient before the pacer has been fully implanted and the implantation surgery completed. This minimizes the need for inconvenient and potentially injurious explantation of the pacer or its associated pacer leads.
One highly desirable function for a pacer system analyzer is to produce a written record of the patient's Electrogram (EGM) signal, as it appears during various stages of the implantation procedure, including paced and unpaced EGM's or before and after adjustments are made to the pacer system. Preferably, this is done by means of a self-contained plotter which provides a facsimile of the desired signal on a strip of paper or other suitable storage medium. From the waveform the attending physician is able to verify and document proper operation of the cardiac system to which the analyzer is connected.
To be suitable for use in a pacer system analyzer it is desirable that a waveform plotter be physically small so as to fit within the analyzer housing, and operable from the internal battery supply of the analyzer so as to not require a separate source of power. Unfortunately, the various plotter assemblies available which meet these requirements have a limited slew rate, or bandpass characteristic, which prevents them from responding to a cardiac signal with sufficient speed to provide a useful and substantially real time display of the signal. The present invention is directed to a data processing system which samples sensed EGM signals to provide digital EGM data point signals useful in providing such a plot.